Musikding the range germainium no gain

[Tadhg]

Hi all,

I bought a treble booster kit from musikding a while ago, put it together and I doesn't work as it should.
I'm ok with saying out loud that I've not got a clue what im doing.

Symptoms:
Passes signal fine when bypassed.
When its engaged I barely make unity, possibly even a signal loss its had to say with the bass roll off.
The 3 position toggle seems to work and the gain pot can reduce volume.
Bias looks  bad to me but I can see what's holding it down.

What is it:
The kit is called the range germainium bought from https://www.musikding.de/The-Range-Germanium-Treblebooster-kit


Modifications to the circuit:
I just wired the footswitch direct and didnt use the pcb for it.
Ive replaced r3 with a 100k pot to give bias adjustment.
Socket for transistor.

Voltage readings:
Battery not connected 9.03v
Batter clip connected 8.96v
On board 9+ 8.15v, gnd 0v
Transistor Collector best I can get with pot all the way up/down is 3v. I can get 7 when i measure from positive terminal of battery and this is where i have about unity gain but i think I'm measuring the other side of the 2ish at the collector at that point.

I've serched for possible solutions and found suggestions to try the transistor the other way around, and the guitar input/output the other way around.

Sorry for the long post. Hopefully I've made sence and given enough information. Thanks for any help in advance.

[ElectricDruid]

Schematic is here: https://www.musikding.de/docs/musikding/rangev2/RangeV2_schalt.pdf

I see from the schematic that they supply various transistors with this kit. Which one did you get? Did you check the pinout carefully? From below, like it says on the schematic?

If you're sure the transistor is fitted correctly, could you post voltages around the transistor please? That'll help us see where the problem is.

[Steben]

This a pnp.... so you need around that mentioned 3V at the collector's connection at the pot.

[antonis]

You should measure about 7.8V on transistor Base (give or take according to particular device leakage current..) and about 8.0V on Emitter..
With +8.15V on board, Collector current should be ( 8.15 - 8 ) / 3900 = 38μA hence Collector volate shouldn't be higher than 380mV..
(I wonder how do you get 3V - unless you have a very leaky BJT)

P.S.
Try it with a brand new battery to see what happens..

edit: I'm getting angry with that 8 close to ) appearing as

[ElectricDruid]

edit: I'm getting angry with that 8 close to ) appearing as

If you break them up by sticking a pair of tags between them, it doesn't do it. 8) See?!

[antonis]

Wowww..!!
(thanx Tom..)

edit: no good..

[duck_arse]

Wowww..!!
(thanx Tom..)

edit: no good..

8)

Code Select Expand

8[i][/i])

or b, or u, or s. (it's gr

[edit :] I'm with antonis and his coffee on this - I rekon it should be made harder to use emotigees instead of so easy it's default step number 8. so there.

[Steben]

You should measure about 7.8V on transistor Base (give or take according to particular device leakage current..) and about 8.0V on Emitter..
With +8.15V on board, Collector current should be ( 8.15 - 8 ) / 3900 = 38μA hence Collector volate shouldn't be higher than 380mV..
(I wonder how do you get 3V - unless you have a very leaky BJT)

P.S.
Try it with a brand new battery to see what happens..

edit: I'm getting angry with that 8 close to ) appearing as

Hi Antonis,
How do you get at that 7.8V instead of 7.15V ? Leakage included?
But it is definitely clear as day that gettin that one lower opens up the output.

Classic rangemaster has 9V at the supply and without any leakage a current about 0.2mA = 200µA. That is a huge difference in bias and resulting amplitude.


@tadhg: can you read the impedance of R2 with a meter?

[antonis]

How do you get at that 7.8V?

9v X (470k/538k) = 7.86V..
(voltage divider bias configuration)

For Collector voltage of 3V, we need 300μA current hence 1.17V drop across 3k9 Emitter resistor..
So, Emitter should sit at 7.83V (9 - 1.17) and Base at 7.6V (a Ge diode forward voltage drop lower)..

For 8.15V (as OP claims for his working battery), Base should sit at 7.2V hence Emitter at 7.43V, resulting into a Collector current of 185μA (8.15 - 7.40)/3900..
So, Collector shouldn't be able to go higher than 1.85V..

Now, for 3V Collector voltage we need "additional" 115μA which is translated to 1.62V total drop across 3k9 Emitter resistor, resulting into 6.53V on Emitter (8.15 - 1.62) and 6.3V on Base..
That calls for an "additional" 900mV voltage drop across 68K resistor, hence a leakage current of about 13μA..
(pas mal..!!)

Edit: I think the issue might be more simple, like an output hitch..
(R6 wrong value, perhaps..)

[PRR]

....I'm with antonis and his coffee on this - I rekon it should be made harder to use emotigees instead of so easy ...

There's another way but it is harder. If you are in Quick Reply, click-through to the full editor. Click "Attachments and other options". Check-box "Don't use smileys."


8)

No, I don't think you will like that. On "some" forum you could make this a personal preference so it DIDN'T auto-smiley unless you enabled it per message. Apparently not offered here.

[Steben]

9v X (470k/538k) = 7.86V..
(voltage divider bias configuration)

Ow yes... 9v

Either way 1.85v at the collector should make for more than unity...

[Tadhg]

OP hear, thanks for all the great replys info.
I'm on nights for the next couple of days so I'm currently operating in a eat, sleep, work world but I've a direction. I'll get at it at over the weekend.

[antonis]

Either way 1.85v at the collector should make for more than unity...

Definitely agree..

Unless "something" (like R6 or next stage input impedance) severely degrades output signal amplitude..

[Steben]

Either way 1.85v at the collector should make for more than unity...

Definitely agree..

Unless "something" (like R6 or next stage input impedance) severely degrades output signal amplitude..

Aha, basic component testing!
Just imagine R2 is 1k instead of 100. R6 is 1K instead of 1M.


@tadhg: have you swapped some transistors?

[Tadhg]

Ok, good news and bad.

The Good.
Finally got back to it, after some messing around I found the ground on my input jack was bad. I've now got a good increase in volume and a very noticeable eq change.
A little embarrassing but when measuring my voltages I had my input wire and ground mixed up, so all them values i gave at the start are complete nonsense.

The bad.
Due to young kids busy house etc the best I can do for a couple of days is try it into a completely clean, solid state practice amp to see if it worked. Ideal place for a TB lol.
Be a couple of days before I get to run it I to my sv20.
Looking forward to see how it does when its hitting a crunchy marshall, I've never run a TB but it seems like the kind of thing I'll like. I'll report back.

Very much appreciate everybodies input, it was working through all the suggestions that lit the bulb.

[Tadhg]

Ok, finally got to try the pedal into my sv20, first with the strat and then the LP.
Even with my s#!+ building skills and the cheapest bits money can buy, it sounds great.
Very happy with it.
Big problam now.... what does a good one sound like?
I've started planning pedal no.2 I'll get some good bits and make a few small changes. Big rabbit hole now.
Thanks again.

[antonis]

Even with my s#!+ building skills and the cheapest bits money can buy, it sounds great.
Very happy with it.
Big problam now.... what does a good one sound like?

Exactly like the one you already have build..

[Steben]

It does not need to be certain amp. TB can be put in front of all things. Like distortion or overdrive pedals.